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BS - Respiratory System > Physiology of the Airway > Flashcards

Physiology of the Airway Flashcards

1
Q

What is the role of the hard palate?

A

It divides the nasal and oral cavities

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2
Q

Where is the hypopharynx?

A

The lower part of the pharynx below the nasal and oral cavities, but before the larynx

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3
Q

What feature of the airway is unique to humans?

A

It is at a right-angle

Whether breathing is through the nose or mouth, it must turn a corner to enter the airways

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4
Q

Why does the hard palate appear white on an MRI scan?

A

it is made of bone

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5
Q

What does not show up well on an MRI scan?

A

soft tissue such as skin and fat

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6
Q

What is the genioglossus?

A

a fan-shaped extrinsic tongue muscle

it forms the majority of the body of the tongue

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7
Q

What is the tensor palatini?

A

a broad, ribbon-like muscle which tenses the soft palate

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8
Q

During nasal breathing, why can’t air pass through the mouth?

A

The lips are closed

The tongue is in contact with both the hard palate and the soft palate

there is no pathway through the mouth

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9
Q

Where does air pass during nasal breathing?

A

through the nasal cavity, nasopharynx, past the soft palate and into the hypopharynx and through to the airway

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10
Q

How does the soft palate change position during mouth breathing?

A

the lips are open and the tongue is contracted away from the soft palate

the soft palate is relaxed and has moved backwards towards the pharynx

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11
Q

What is the effect of gravity on the structures of the body?

A

Gravity means that all the structures in the body have weight

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12
Q

Why does the tongue muscle have tonic activity?

A

It is always contracting to keep the airway open when lying down

the tongue must be lifted forwards off the back of the pharynx to keep the airway open

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13
Q

What type of activity is possessed by all the muscles in the airway?

A

they have tonic and phasic activity

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14
Q

Why do the muscles in the airway have phasic activity?

A

This is muscle contraction that occurs with the phases of breathing

all the muscles contract more during inspiration to increase the diameter of the airway and relax a bit more during expiration

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15
Q

why does the soft palate have tonic activity?

A

It is contracting all of the time to control airway activity

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16
Q

What is the pharyngeal dilator reflex?

A

a neuronal reflex in the airway

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17
Q

What are the components of the pharyngeal dilator reflex?

A

pressure receptors

trigeminal nerve

brainstem

vagus nerve

pharyngeal muscles

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18
Q

what is the role of the pressure receptors in the mucosa of the pharynx?

A

they are sensitive to the air pressure above them

if the air pressure changes, they send signals of varying rates along the trigeminal nerve

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19
Q

What is the role of the brainstem in the pharyngeal dilator reflex?

A

it processes information received from the trigeminal nerve

it then sends an impulse down the vagus nerve to the pharyngeal muscles

this causes the pharyngeal muscles to contract or relax

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20
Q

What happens when the pharyngeal muscles contract or relax?

A

It changes the pressure in the airways

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21
Q

What is the action of the pharyngeal muscles when there is a low pressure in the airway and why?

A

When the pressure is low, there is increased effort by the lungs to move air through the airway

Pharyngeal muscles contract more to open the airway up

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22
Q

How long does the pharyngeal dilator reflex take and when does it occur?

A

50 ms

it is occurring all the time as the pressure of the pharynx is constantly monitored and the diameter of the airway changed accordingly

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23
Q

What reduces the efficiency of the pharyngeal dilator reflex?

A

drugs that slow the brainstem down

includes alcohol, sedative drugs and general anaesthetic

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24
Q

Why is the pharyngeal dilator reflex less efficient at night?

A

During sleep the brainstem becomes slower

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25
Q

What is sleep disordered breathing?

A

the change in the way the movement through the airway changes during sleep

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26
Q

What % of people snore and suffer from sleep apnoea?

A

25% of people snore

10% of people have sleep apnoea

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27
Q

What happens to breathing in sleep apnoea?

A

Patients will stop breathing for periods of 10 seconds during sleep

This misses around 2 or 3 breaths

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28
Q

What is the most common cause of ceased breathing in sleep apnoea?

A

closure of the airway

there is a very narrow gap between the soft palate and the pharynx

if the muscles relax slightly then the airway is completely blocked off

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29
Q

In which types of patients is sleep apnoea more common?

A

obese patients and after consumption of alcohol

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30
Q

What factor in obese patients can determine whether they have sleep apnoea?

A

the circumference of the neck

the compression of fat in the neck means the muscles have to work harder to keep the airways open

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31
Q

Which components are measured on a polysomnograph?

A

tidal volume

movement of the ribcage

movement of the abdomen

pharyngeal pressure

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32
Q

What does the tidal volume trace look like on a polysomnograph for a sleep apnoea patient?

A

regular breaths of around 500ml begin to fade and eventually stop

breaths stop for around 15 seconds (one apnoea)

there is a large breath as the patient recovers

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33
Q

How does the movement of the ribcage and the diaphragm change after obstruction in sleep apnoea?

A

the ribcage and the abdomen move in sync with each other during normal breathing

after obstruction, they begin to oppose each other

the ribcage muscles contract but the diaphragm can’t, due to the airway being blocked

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34
Q

why is the movement of the abdomen measured on a polysomnograph?

A

it shows the extent to which the diaphragm is working

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35
Q

What happens to pharyngeal pressure in a sleep apnoea patient?

A

with each breath after obstruction, pharyngeal pressure decreases

pharyngeal receptors fire more and more to try and make the brain do something about this

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36
Q

Why do patients with sleep apnoea not die?

A

When they stop breathing, they almost wake up

Something brings them back to a lighter level of sleep where the brain can gain control of the airway

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37
Q

What causes the arousal from deep sleep in sleep apnoea patients?

A

It is thought to be the pharyngeal receptors sending increasingly intense impulses to the brain

It may be due to oxygen levels starting to fall or carbon dioxide levels starting to rise

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38
Q

How is sleep apnoea quantified and what is “normal”?

A

quantified by the number of times the process occurs within one hour

“normal” is up to 5 times per hour

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39
Q

What are the symptoms of sleep apnoea?

A

snoring and daytime somnolence

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40
Q

Why do sleep apnoea patients experience daytime somnolence?

A

They never get any deep sleep so feel very tired in the morning

every time they wake up, adrenaline is released

this causes a small amount of sympathetic activity

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41
Q

What are the treatments for sleep apnoea?

A
  1. weight loss

2. CPAP machine

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42
Q

What is the CPAP machine?

What is the problem with this treatment method?

A

It applies positive pressure to the nose that forces the soft palate forwards during the night to prevent obstruction

the compliance rate is very low

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43
Q

Where is airway lining fluid produced?

A

ciliated epithelial cells and goblet cells

44
Q

What are the conducting passages of the respiratory system lined with?

A

mucosa

a tissue which produces mucous

45
Q

What do the ciliated epithelial cells look like in the nose and pharynx?

A

pseudostratified

this is a single layer of cells that appears as multiple layers

the cells are tall so you cannot see the junctions between them, only the nuclei

46
Q

What do the ciliated epithelial cells look like in the trachea and bronchi?

A

they become wider columnar cells

47
Q

What do the ciliated epithelial cells look like in the bronchioles?

A

the cells are cuboidal

48
Q

How do the cells change in appearance as you go down the airway?

A

cells are ciliated all the way down to the bronchioles

they become progressively shorter

49
Q

What is the diameter of the bronchioles?

A

they are passages that are less than 1 mm in diameter

50
Q

What do goblet cells produce and why?

A

They produce mucin

They produce mucin in response to anything that irritates the airway

51
Q

What are the 2 layers of fluid in the airway?

A

the periciliary layer

the mucous layer (gel-layer)

52
Q

What is the periciliary layer?

A

It is saline

It is water with some salt solution within it and has low viscosity

53
Q

What is the purpose of the mucous layer?

A

It is jelly-like in consistency and will trap any particles that are inspired

54
Q

What is the purpose of the periciliary layer?

A

It allows the mucous layer to be moved towards the top of the lung

It will be coughed out by expiration or swallowed

55
Q

How do cilia within the periciliary layer move?

A

They move sideways, backwards and then flick forwards

As they flick forwards they touch the underneath of the mucous layer and can move it along

56
Q

At what rate does the mucous move along the airway?

How often do the cilia beat?

A

it moves along by 4mm per minute

the cilia beat 12 - 15 times per second

57
Q

how does tobacco smoke affect the cilia?

A

It contains hydrogen cyanide which poisons the cilia and stops them from working effectively

This leads to a smoker’s cough

58
Q

Why is a smoker’s cough worse in the morning?

A

During the night the cilia recover and bring all the previous day’s mucous up to the top of the lung

59
Q

Other than tobacco smoke, what else can affect the cilia?

A

Anaesthetics stop the cilia from working, causing chest infections to occur soon after

Pollution and infections can affect the cilia

60
Q

What are the functions of the airway lining fluid?

A

Humidification and warmth (conditioning)

Airway defence

61
Q

Why does air need to be humidified and warmed by the time it reaches the alveoli?

A

The air must be 37 degrees and humid

The cells of the alveoli are very thin and delicate

If the air is not conditioned, the alveoli will dry out and the cells will become damaged

62
Q

Why is nasal breathing better for humidification than mouth breathing?

A

As air goes through the nasal cavity, the meatuses mix the air up and increase the efficiency of evaporation from the lining fluid

There is also more distance to travel

63
Q

How does the airway act as a “Heat and Moisture Exchanger”?

A
  1. air enters the nose and water evaporates from the airway lining fluid in the nose and pharynx
  2. the mucosa in the pharynx is cooled and dry
  3. during expiration, the air that passes through the airways is 37 degrees

the water will condense on the cooler mucosa as it leaves the body

  1. the same water and heat are reused during the process
64
Q

How does the lung adapt to cope with different amounts of humidity in the air?

A

it changes the thickness of the mucous layer

65
Q

What happens to the mucous layer in high humidity?

A

Water is absorbed by the mucous layer which swells up and holds the water

66
Q

How is the constancy of the mucous layer maintained as humidity changes?

A

Epithelial cells detect when the movement of the cilia is impeded or becomes too free

the physical movement of the cilia causes the epithelial cells to secrete Cl- through a chloride ion channel into the pericilliary layer

Na+ follows by passive diffusion, followed by water

This changes the thickness of the layer

67
Q

How does the airway lining fluid contribute to airway defence?

A
  1. expectoration

2. the muco-ciliary escalator moves particles back towards the top of the lungs and out of the body

68
Q

What is cystic fibrosis caused by?

A

a genetic abnormality of the cystic fibrosis transmembrane regulator gene

This codes for the CFTR protein

69
Q

What is the CFTR protein?

A

a chloride channel present on epithelial cells

70
Q

What is the affect of cystic fibrosis on the airway lining fluid?

A

it affects the regulation of chloride in the airway lining fluid

this causes the mucous to become too viscous

71
Q

What is the side effect of mucous becoming too viscous?

A

CF patients cannot fight off infection as pathogenic particles cannot be moved

72
Q

What other factor makes cystic fibrosis patients more prone to infection?

A

Defensins are natural antibiotics in the airway lining fluid

In CF patients, the defensins do not work properly

this makes them more prone to infection

73
Q

What is the most common presenting factor of cystic fibrosis?

A

a chest infection of a small baby under the age of 1

74
Q

What is the smallest particle that can be seen by the naked eye?

A

Particles that are bigger than 5 micrometres can be seen

Particles under 5 microns can only be seen if there are many of them together - this is smoke

75
Q

What is the size of a very large particle and where are they deposited?

A

> 8 micrometres

deposited in the nose and pharynx

76
Q

What is the size of a large particle and where are they deposited?

A

3 - 8 micrometres

deposited in the large airways

77
Q

By which mechanism do large and very large particles enter the airway?

A

Inertial impaction

78
Q

What is inertial impaction?

A

particles will hit the back of the pharynx by inertial impaction

the particle has inertion which keeps it moving in a straight line when it tries to turn a corner

benefit of having a right-angled respiratory tract

79
Q

What size is a small particle and where are they deposited?

A

0.5 - 3 micrometres

deposited in the bronchioles

80
Q

By which mechanism are small particles prevented from entering the airway?

A

sedimentation

the weight of the particles causes them to drop out of the air onto the wall of the bronchioles

mucous in the bronchioles expels them out of the body

81
Q

What size is a very small particle and where are they deposited?

A

<0.5 micrometres

they are not deposited, they are exhaled again by diffusion

82
Q

What are examples of very large, large, small and very small particles?

A

very large - pollen, sawdust

large - fungal spores

small - particulate pollution, stone dust, asbestos

very small - smoke (incl. cigarettes)

83
Q

How does gravity affect the number of particles in the air?

A

Gravity pulls most of the dust in the air down to the floor so there are very few particles in the air

without gravity, all of the particles that are formed would stay in the air forever

84
Q

What is the benefit of having no gravity?

A

sedimentation does not occur as the particles have no weight

this is beneficial as it means more particles are expired

85
Q

In inhaled drug delivery, by how much do the particles in the spray vary in size?

A

particles vary in size from 1 - 35 micrometers

86
Q

In inhaled drug delivery, what is a large particle and where are they deposited?

What is the problem with this?

A

> 5 micrometers

they are deposited on the pharynx or in the large airways

they do not reach the bronchioles so are ineffective at treating most conditions

87
Q

What is the side effects of inhalers containing large particles?

A

they are deposited on the pharynx which leads to side effects

using a steroid inhaler leads to a sore throat and infections due to the steroid on the pharynx

88
Q

In inhaled drug delivery, what is a medium particle and where are they deposited?

A

1 - 3 microns

they are deposited in the small airways

89
Q

In inhaled drug delivery, what is a small particle and where are they deposited?

A

0.5 - 1 microns

they are deposited in the alveolus

90
Q

What are the potential uses of large, medium and small particles in inhaled drug delivery?

A

large - hayfever

medium - copd, asthma

small - absorption into the blood

91
Q

What are the 3 non-immunological pulmonary defences?

What is significant about them?

A
  1. physical barrier and removal removes 99.9% of inhaled pathogens
  2. chemical inactivation
  3. alveolar macrophages

all of these defences are non-specific

92
Q

what is the role of lysozyme within the mucous layer?

A

it is an enzyme that lyses cells by breaking down their cell walls

93
Q

what is the role of protease enzymes within the mucous layer?

A

they break down proteins

e.g. elastase

94
Q

what is the role of anti-protease and where is it found?

A

protease enzymes will also break down proteins found in our cells

anti-protease is found on the surface of epithelial cells

it prevents protease from damaging the cell if it gets too close

95
Q

what is an example of an antimicrobial peptide within the mucous layer?

A

human beta defensins

96
Q

what is the role of alveolar macrophages?

A

they leave the blood and come onto the surface of the alveolus

they ingest any particles they find, including pollutants and pathogens

they are the last line of non-specific defence

97
Q

What is the difference between humoral and cell-mediated immunity?

A

humoral immunity involves chemicals

cell-mediated immunity involves cells

98
Q

What components are involved in humoral immunity in the airway and where are they found?

A

IgA - nose and large airways

IgG - small airways

IgE - allergic disease

99
Q

How are cilia involved in immunological defence?

A

Cilia on the epithelial cells can recognise bacteria

100
Q

What happens once the bacteria is detected?

A

cytokines are released and an inflammatory cascade is initiated

the inflammatory response leads to a chest infection and potentially pneumonia

101
Q

What are the components of cell-mediated immunity in the respiratory tract?

A

epithelial cells

macrophages

neutrophils in infection

eosinophils in allergy

102
Q

What is the effect of carbon monoxide on the airway?

A

decreased oxygen carriage

103
Q

what is the effect of nitrogen oxides on the airway?

A

airway irritation and asthma

104
Q

what is the effect of ozone on the airway?

A

airway irritation and cough

105
Q

what is the effect of particulate matter on the airway?

A

lung and systemic inflammatory response

106
Q

what diseases is air pollution associated with a risk of?

A 
asthma
pneumonia
stroke
heart attack
type 2 diabetes

BS - Respiratory System (20 decks)

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